.
REGION I MORNING REPORT PAGE 2 FEBRUARY 8, 1995
Licensee/Facility: Notification:
Niagara Mohawk Power Corp. MR Number: 1-95-0020
Nine Mile Point 1 Date: 02/08/95
Lycoming,New York SRI PC
Dockets: 50-220
BWR/GE-2
Subject: PLANT SHUTDOWN DUE TO PROBLEMS WITH AGASTAT RELAYS
Reportable Event Number: N/A
Discussion:
At 8:30 p.m., on February 7, 1995, Nine Mile Unit 1 commenced a normal
plant shutdown after identifying that three (of eight) Agastat relays in
the power supplies for the analog trip subsystem (ATS) of the reactor
protection system (RPS) were not functioning. The specific relays
provide annunciation on power supply failure. Several weeks earlier
during scheduled fuse replacement, it was noted that the ATS power
available indicating light in the control room did not extinguish when
expected. A work order was initiated to repair the system; the failed
relays were found yesterday during troubleshooting activities.
ATS is the portion of RPS that includes the relays associated with the
various parameters that feed the protective circuitry to initiate
protective actions, such as reactor scram or core spray actuation. The
three relays that failed were 24 VDC Agastat relays, model FGPBC750. The
relays are normally energized, and deenergize to trip. The ATS cabinets
were installed circa 1980, and most of the relays are original equipment.
Investigation continues to determine whether other 24 VDC relays which
supply RPS trip, emergency core cooling system initiation, and
containment isolation signals, or the other Agastat 110 VAC and 125 VDC
relays in the ATS cabinets are also affected. Preliminarily, NMPC feels
that aging coupled with the temperature inside the cabinets caused the
failures.
NMPC did not declare any equipment inoperable, but took what they
considered prudent action to comply with the most restrictive limiting
condition for operation (LCO) on potentially affected emergency core
cooling system components. This required initiation of a shutdown within
one hour and cold shutdown within the next ten hours. As of the time of
this report, the reactor coolant system is at 178 degrees F and the
shutdown cooling system is in operation. The plant was scheduled to
begin a refueling outage on February 11, 1995.
Regional Action:
The resident inspectors will continue to follow this issue.
Contact: Lawrence Doerflein (610)337-5378
Barry Norris (315)342-4041